Display apparatus and image signal processing apparatus

ABSTRACT

To attain high image quality such as high resolution and high dynamic range in a display apparatus for irradiating light generated by a light source onto a light modulating element and for forming a display image plane from the light transmitted through or reflected by the light modulating element.  
     The apparatus is configured to control irradiation light quantity, in which the high image quality is provided by an unit for temporarily storing display signal, an unit for adjusting signal under an analog state, a unit for differentiating a rate of change in light quantity at the time of increase and at the time of decrease and a unit for controlling light quantity to resemble hysteresis.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a display apparatus as well as asignal processing apparatus for a display apparatus that is suitable forapplication to a large image plane/highly accurate display apparatussuch as a liquid crystal display and a projector, etc.

[0003] 2. Related Background Art

[0004] Advent of the multimedia age brings display apparatus to all thescenes, and since projection type display apparatus is efficientcompared with other systems in particular, front projectors are incommon use for presentations, etc. and rear projectors are in common usefor domestic theaters.

[0005] In recent years, CRT projection is being replaced by a projectorin a liquid crystal panel system and a DMD (digital mirror device, forwhich reference should be made to Japanese Patent Application Laid-OpenNo. 10-78550) method modulating light quantity by changing angles of anmirror which are turning to spread because they are appropriate forproviding high luminance and highly delicate accuracy.

[0006] However, these projection-type display apparatuses is inferior toCRT display tubes in general use in terms of picture quality, and forhigh picture quality display (display demanded for quality feeling),users tend to use CRT display tubes even when the image plane size issmall. High picture quality (quality feeling) herein referred to is highdynamic range (capability of high contrast and high gradation display).

[0007] Since a CRT, luminance of which can be modulated with electronbeam intensification, etc., dynamic range can realize up to around1000:1 in the case where only a particular range (a partial region)displays white, etc. Accordingly, its potentiality can make whitebrighter and black darker to realize excellent picture quality. However,in case of a CRT system, the size thereof is around 40 inches at largestdue to limitation in a tube, etc., giving rise to a problem that thereexists a high degree of technological difficulty for larger sizes.

[0008] On the other hand, in a projection-type display apparatus, a CRTsystem is traded off in terms of its engine size, brightness and highaccuracy, etc, and as described above, a liquid crystal system as wellas a DMD system is suitable for high luminance and high accuracy isrecently in a main stream. In these cases, the liquid crystal and theDMD are assigned to play roles of a light modulator, and a lampilluminates the above described liquid crystal device or DMD to beenlarged for projection by a projection optical system. Accordingly, theabove described dynamic range is determined wit the dynamic range mainlyprovided by the liquid crystal device or DMD.

[0009] The practical dynamic range of the above described device isapproximately 300 to 400:1 for liquid crystals and approximately 500 to600:1 for DMDS. Accordingly, they used to have a problem that there is along way to win against the above described CRT system in terms of onepoint of high picture quality (high dynamic range).

[0010] In addition, a direct-view-type LCD likewise used to have aproblem that its dynamic range is low, compared with the CRT.

[0011] Incidentally, as background documents of the present application,Japanese Patent No. 2643712, Japanese Patent Application Laid-Open No.6-102484 and Japanese Patent Application Laid-Open No. 11-65528 andJapanese Patent Application Laid-Open No. 6-167717 are nominated.

SUMMARY OF THE INVENTION

[0012] An objective to be solved by the present invention application isto realize high picture quality in a projection-type display apparatusor direct-view-type apparatus irradiating lights to a light modulatingelement to construct display image planes by its penetrating light orreflected light.

[0013] Another objective of the mode of embodiments of the presentapplication is to provide a system to attain high picture quality of ahigh dynamic range to be attached to features of large image plane andhigh accuracy of the projection-type display apparatus.

[0014] Moreover, the above described system is to attain the abovedescribed objective with an existing device, which might be a liquidcrystal device and DMD having levels thereof, in combination, and is alow-cost and practical system.

[0015] In addition, the objective includes providing a system to attainhigh picture quality of high dynamic range to be attached to features ofhigh degree of resolution in a direct-view-type liquid crystal displayapparatus provided with back light.

[0016] One aspect of the present invention application is constructed asfollows.

[0017] A display apparatus irradiating light generated by a light sourceonto a light modulating element and forming a display image plane withthe light transmitted through or reflected by the light modulatingelement, comprising:

[0018] input image calculating means for performing predeterminedcalculation according to an input display signal;

[0019] light quantity controlling means for controlling light quantityirradiated onto the above described light modulating element accordingto a result of the above described calculation; and

[0020] a memory for storing display signal subjected to the abovedescribed calculation by the input image calculating means, and foroutputting thereafter the display signal to the above described lightmodulating element.

[0021] Here, the display signal is referred to as an image signal and animage data to be inputted.

[0022] In this invention, a memory is provided so as to temporally storethe display signal after calculation, and therefore, even if lightquantity control takes time, it will become possible that the signal tobe inputted to the light modulating element are easily brought intosynchronization with the light quantity control corresponding with thesignals.

[0023] Another aspect of the present invention is constructed asfollows.

[0024] A display apparatus irradiating light generated by a light sourceonto a light modulating element inputting a modulated signal formed byconverting display signal inputted in an analog state into digitaldisplay signals and thereafter subjected to the converted digitaldisplay signal to a predetermined processing, and forming a displayimage plane from the light which transmitted through or reflected by thelight modulating element, comprising:

[0025] input image calculating means for performing predeterminedcalculation according to the display signal;

[0026] light quantity controlling means for controlling light quantityirradiated onto the above described light modulating element accordingto a result of the above described calculation; and

[0027] an adjusting circuit for adjusting display signal according to aresult of the above described calculation,

[0028] wherein the above described adjusting circuit adjusts displaysignal before the conversion of the display signal in the abovedescribed analog state into the digital display signal.

[0029] Incidentally, in this invention, the display signal to undergocalculation may be in an analog state or may be those having undergonedigital conversion.

[0030] In addition, adjustment referred to herein is exemplified byamplification.

[0031] In addition, prior to inputting to the modulating element, signalmay be converted into analog display signal again after that isconverted from analog display signal to digital display signal andundergo a predetermined processing.

[0032] In addition, another aspect of the present invention isconstructed as follows.

[0033] A display apparatus irradiating light generated by a light sourceonto a light modulating element and forming a display image plane fromthe light transmitted through or reflected by the light modulatingelement:

[0034] input image calculating means for performing predeterminedcalculation according to the display signal; and

[0035] light quantity controlling means for controlling light quantityirradiated onto the above described light modulating element accordingto a result of the above described calculation,

[0036] wherein the above described light quantity controlling means setsa change rate when the above described light quantity is decreased to asmaller one than a change rate when the light quantity is increased.

[0037] The change rate referred to herein is in particular the oneobtained by dividing the difference between the light quantity at startof change and the light quantity at completion of change with time fromstart of change to when to reach a desired light quantity.

[0038] In addition, another aspect of the present invention isconstructed as follows.

[0039] A display apparatus irradiating light generated by a light sourceonto a light modulating element and forming a display image plane fromthe light transmitted through or reflected by the light modulatingelement, comprising:

[0040] input image calculating means for performing predeterminedcalculation according to an input display signal; and

[0041] light quantity controlling means for increasing or decreasing alight quantity irradiated onto the above described light modulatingelement step by step according to a value determined by result of theabove described calculation,

[0042] wherein a threshold value at which the above described lightquantity controlling means increases a first stage being a predeterminedstage to a second stage by increasing the above described light quantityby one stage corresponding with a value determined by the abovedescribed calculation is different from a threshold at which the abovedescribed second stage is decreased to a stage with less light quantity.

[0043] Here, the above described light quantity controlling meanspreferably set so as to increase the above described light quantity fromthe above described first stage to the above described second stage whenthe value determined by the above described calculation changes in thefirst direction to exceed the first threshold value, and so as todecrease the above described light quantity from the above describedsecond stage to a stage with less light quantity when the valuedetermined by the above described calculation changes in the seconddirection being opposite against the above described first direction toexceed the second threshold value set in the side of the above describedsecond direction than the above described first threshold value. Inaddition, here the stage of the above described low light quantity beingthe above described first stage can be controlled easily.

[0044] In addition, the aspects of the present invention described abovesuitably have adjusting circuits to adjust display signals correspondingwith outcomes of the above described calculation. In addition, in thecase where in the above described input image calculating means, amemory to store and thereafter output display signals having become anobject for calculation toward the above described light modulatingelement, positions where the memory is provided can be appropriatelyset. For example, it can be provided in the preceding stage of theadjusting circuit.

[0045] Incidentally, various setting is possible for adjustment executedby this adjusting circuit, and in case of executing amplification, forexample, a construction to amplify display signals at an amplifyingratio approximately in inverse proportion to light quantity illuminatedto the above described light modulating element can be suitably adopted.

[0046] In addition, in the aspects of the present invention describedabove, such constructions that the above described calculation could becalculation to give maximum luminance in the above described displaysignals inputted within a predetermined period or could be calculationto give a certain number of data exceeding a predetermined luminance inluminance data that the above described display signals to be inputtedwithin a predetermined period include can be suitably adopted. Here, asthe predetermined period, 1 frame time or 1 field time in the case where1 frame is constructed with a plurality of fields can suitably beadopted. In addition, for a section to count the above describedluminance data, luminance data corresponding with one pixel is would bebetter to count as one luminance data.

[0047] In addition, the above described aspects of the present inventionfurther have sensors to detect light quantity illuminated onto the abovedescribed light modulating element, suitably wherein the above describedlight quantity controlling means control the above described lightquantity based on the above described calculation results and resultsdetected by the above described sensors.

[0048] In addition, the display signals are adjusted corresponding withthe above described calculation results, the adjusting circuit cansuitably adopts a construction to execute the above described adjustmentcorresponding the above described calculation results and the resultsdetected by the above described sensors.

[0049] In addition, the aspects of the present invention described abovecan suitably adopt a construction to comprise irradiation light quantitychanging quantity setting means to set changing quantity or change rateof the above described irradiation light quantity.

[0050] In addition, the aspects of the present invention described abovecan suitably adopt such construction that the above described lightquantity controlling means are means to be disposed between the abovedescribed light source and the above described light modulating elementto control light quantity to be irradiated to the above described lightmodulating element from the above described light source or suchconstruction being means to control voltages or currents to be suppliedto the above described light source.

[0051] Incidentally, the aspects of the present invention describedabove can be used appropriately in combination.

[0052] In addition, the present application includes an invention of theimage signal processing apparatus to be used in the above describeddisplay apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053]FIG. 1 is a block diagram showing electric system related to afirst embodiment;

[0054]FIG. 2 is an explanatory view showing display examples accordingto the present invention;

[0055]FIG. 3 is a block diagram showing a processing flow according to afirst embodiment of the present invention;

[0056]FIG. 4 is a flow chart according to the first embodiment of thepresent invention;

[0057]FIG. 5 is a block diagram showing a second embodiment;

[0058]FIG. 6 is a block diagram showing a third embodiment;

[0059]FIG. 7 is a flow chart showing a processing method of the thirdembodiment;

[0060]FIG. 8 is a block diagram showing a fourth embodiment;

[0061]FIG. 9 is an explanatory view showing a processing flow of a unitof calculating irradiation modulating factor of a fourth embodiment;

[0062]FIG. 10 is a schematic view showing a construction of an opticalsystem for a liquid crystal projector related to a fifth embodiment ofthe present invention;

[0063]FIG. 11 is a schematic view showing a variation of the lightmodulator portion in FIG. 10;

[0064]FIG. 12 is a flow chart showing operation of the light modulatorin FIG. 11;

[0065]FIG. 13 is a construction view showing an optical system of a DMDprojector related to a sixth embodiment of the present invention; and

[0066]FIG. 14, composed of FIGS. 14A and 14B, is a block diagram showinga construction of a electric system of a DMD projector related to aseventh embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] A display apparatus according to a preferred embodiment of thepresent invention is characterized in that it is provided with means toadjust light quantity to illuminate a light modulator (a liquid crystaldevice and a DMD), a circuit for processing a signal to the lightmodulator based on the above described illuminated light quantity andmeans for writing in that signal.

[0068] A projection-type display apparatus related to a preferableembodiment of the present invention is, as its features, providedbetween a light source and a light modulator (a liquid crystal deviceand a DMD) means (irradiation light quantity modulating means) to adjustlight quantity to illuminate the above described light modulator, acircuit for processing a signal to the light modulator based on theabove described illuminated light quantity and means for writing in thatsignal.

[0069] The above described signal processing circuit may compriseamplifying means to amplify an input image signal at an amplifying ratioin inverse proportion to the above described light quantity or lightquantity controlling signals.

[0070] According to the present invention, provision of irradiationlight quantity modulating means to adjust light quantity illuminatedonto the light modulator can make it possible to illuminate a dark imageplane with low light quantity and a bright image plane with high lightquantity, and consequently to realize a dynamic range higher than in thecase where the light modulator is illuminated with constant lightquantity.

[0071] In addition, controlling the light quantity and the signalamplifying ratio in approximately inverse proportion by means of thesignal processing circuit to become an adjusting circuit to adjust theabove described display signals and the signal write-in means, highdynamic range can be realized while maintaining display luminance in anintermediate gradation at a constant.

[0072] The above described irradiation light quantity modulating meansmay be the one to directly control a light source generating a light tobe caused to illuminate the light modulator or the one to be providedbetween the light source and the light modulator to modulatetransmissivity of the irradiation light quantity. As the former, meansto control voltages or currents to be supplied to the light source andas the latter the one which has means to convert a light flux from thelight source into a polarized light flux together with the polarizingplate or a phase plate disposed capable of rotation in combination canbe exemplified.

Embodiments

[0073] With reference to the drawings, embodiments of the presentinvention will be described below.

Embodiment 1

[0074]FIG. 1 shows a block diagram of a signal processing apparatusrelated to an embodiment of the present invention.

[0075] In FIG. 1, reference numerals 18, 17 and 16 denote liquid crystalpanels in correspondence with R, G and B color display respectively,reference numeral 54 denotes a driver circuit to supply each liquidcrystal panel with applying signals and power source, reference numeral55 denotes a DA converter and reference numeral 56 denotes a memory. Thememory 56 holds current display data as well as data to be displayed inthe next frame and the like. Reference numeral 57 denotes a DSP unit toexecute not only processing such as gamma adjustment, conversion ofinterlace signals to non-interlace signals, resolution conversion in thecase where the pixel amount of liquid crystal panel currently in usedoes not corresponds with the pixel amount of the input signal and coloradjustment, etc. but also operation to calculate signal levels ofrespective colors for irradiation light quantity control. Referencenumeral 58 denotes a timing generator circuit and reference numeral 59denotes a remote controller to execute power source ON-OFF switching aswell as respective kinds of settings. Reference numeral 60 denotes acontrol panel for receiving signals from the remote controller andexecuting respective kinds of input signal switching, etc. and referencenumeral 61 denotes a driver for ultrasonic motor for modulating(controlling) irradiation light quantity and reference numeral 62denotes an ultrasonic motor. Reference numeral 63 denotes amicrocomputer to which the memory 56, the DSP unit 57, the timinggenerator circuit 58, the control panel 60, the USM driver 61, the powersource 66 and a ballast for a lamp 64, etc. are brought into connectionvia a bus to control those respective blocks. The lamp 65 is connectedwith the ballast 64. Reference numeral 67 denotes an A/D converter andreference numeral 68 denotes a switch. Reference numeral 69 denotes asignal processing circuit, which executes signal processing such asdecoding NTSC signals, noise reducing processing, band limitationfiltering and signal level adjustment, etc. Reference numeral 71 denotesa PC (personal computer) input terminal and reference numeral 72 denotesan NTSC input terminal, but in the present block diagram, only an analoginput signal is indicated, but without limitation thereto, it goeswithout saying that input terminals such as LVDS and TMDS, etc. and a D3terminal for a digital TV, etc. may be provided to function effectively.Reference numeral 75 denotes a sound input terminal, reference numeral76 denotes a sound switching switch, reference numeral 70 denotes asound processing circuit, reference numeral 73 denotes a speaker andreference numeral 74 denotes an AC inlet.

[0076] With reference to an electric block diagram in FIG. 1, basicoperation on driving the irradiation light quantity modulation system ofthe present embodiment (operation of a system to write signals into aliquid crystal panel corresponding with a maximum luminance leveldetermined by image signals) will be described.

[0077] Signals inputted from the input terminals 71 and 72 are convertedinto digital signals via an AD converter 67 and temporally stored intothe memory 56. At that time, the maximum luminance level at that frameis calculated, and currents or voltages to be supplied to the lightsource via rotation angle of the polarizing plate or phase plate orballast 64 with which irradiation light quantity corresponding with thatmaximum luminance level is obtained are calculated, and signals torealize a desired luminance at each pixel when the irradiation light inthat light quantity is illuminated onto the panels are calculated andwritten. Signals from the memory 56 are read out in synchronization withlight quantity control corresponding with signals being stored. A methodof calculation of the above described maximum luminance level will bedescribed later.

[0078] With reference to FIG. 2, a relationship between light quantitymodulation and signal gains in respective display images will bedescribed.

[0079] (a) of FIG. 2 shows images at the time t1 in which the sun iscoming down below a mountain while the recess of a mountain and the skyare becoming dark. Numerical values in FIG. 2 represent luminance levelsof that image. (b) of FIG. 2 shows an image after time has lapsed than(a) of FIG. 2, and the picture gets further darker subject to sunset.The peak at that time reaches 80% level compared with the precedingframe (a). The case (c) where time has further lapsed to enter nightwith the moon appearing in the sky so that the maximum luminance levelreaches 30%.

[0080] Here, with respect to each image data, for (a) a light of 100%level is illuminated to the liquid crystal panel, for (b) a light of 80%level and for (c) a light of 30% level is illuminated. The displayedimages for respective cases will become (a′), (b′) and (c′). Here, thereduced portion of the irradiation light is supplemented by amplifyingsignals. In (a′) of FIG. 2, due to absence of drop in light quantity,the amplifying ratio is set at 1, in (b′) of FIG. 2, the amplifyingratio is set at 1.25 times and in (c′) of FIG. 2, the amplifying ratiois set at 3.3 times. They will result in (a″), (b″) and (c″) of FIG. 2so that display luminance is maintained.

[0081] As described so far, combination of amplifying light quantitymodulation and signals will enable improvement in dynamic range bybroadening a displayable gray scale near a black level while maintainingdisplay luminance.

[0082] With the dynamic range of the liquid crystal being 200:1, blacklevels of luminance level of not more than 0.5 cannot be displayed when100% light quantity is illuminated, but according to the presentembodiment, as the entire image plane is getting darker, the displayablerange of the black level gets broader, and therefore further enhancedblack display can be realized. In the case where the entire image planeis bright or is influenced by reflection lights from external lights,the recognition level on delicate difference of the black level coulddrop to human eyes, and reproducibility of black will not be soremarkable. However, as a scene gets darker, that reproducibilitybecomes important, but that is matched the above described technology,and in case of the above described embodiment, the dynamic range will bepractically improved to reach approximately 660:1.

[0083] In case of such a source with a lot of dark image scenes as infilms, etc., the present effect is enormous, and images with goodreproducibility of black and with improved dynamic range have becomeavailable.

[0084] In the present embodiment, a method to improve the dynamic rangewith the reduced portion of the irradiation light being supplemented byamplifying signals while display luminance is maintained has beendescribed, a method to cause the signal gain to exceed the reducedportion of the irradiation light in order to use the dynamic range ofthe LCD effectively is effective.

[0085] Next, how to calculate a maximum luminance from image signals infurther particular, moreover how to calculate a desired irradiationlight quantity level from that calculated maximum luminance data, andhow to determine an amplifying ratio of image signals from theirradiation light quantity level will be described in detail.

[0086] Maximum luminance is calculated by sequentially comparing inputimage data inside 1 frame or 1 field. In this case, since comparison onevery pixel could lead to miscalculation of maximum luminance due toinfluence of noises, etc., it is also effective that the maximumluminance is calculated by comparing values undergoing averaging (oraveraging with weight) several pixels in the vicinity of the targetpixel as respective pixel values.

[0087]FIG. 3 is a block diagram to describe processing inside a DSP, andFIG. 4 is a flow chart.

[0088] Based on an input signal 301 inputted from an input end 301, aluminance distribution calculating unit 302 calculate the maximumluminance (S402) as described above, and based on that result,irradiation light quantity is determined by an irradiation lightquantity calculating unit 303 (S403). In addition, a unit of calculatingquantity of controlling light quantity 304 determines the controllinglight quantity (S404). Next, a unit of calculating amplifying ratio 305determines an amplifying ratio so as to maintain the projected displayluminance (S405), and an image signal amplifying unit 306 being writingsignal conversion means amplifies the input signals 301, which isoutputted as output signals 307.

[0089] Incidentally, for a circuit for writing signal conversion, amultiplier may be used or a conversion table (LUT: Look Up Table) maywith which conversion features can be set further in detail may be used.In addition, a dynamic range adjusting circuit already existing in animage signal processing circuit (for example the signal processingcircuit 69 in FIG. 1 and the image signal processing unit 508 in FIG. 5)may be used.

Embodiment 2

[0090] In Embodiment 1, a construction using a liquid crystal panel asthe light modulating element has been described, but in the presentembodiment, as the light modulating element, a light modulating element,also known as a DMD, displaying images by integrating micromirrors andcontrolling reflecting directions of irradiation lights with respectivemirrors is used. Description on portions in common with Embodiment 1will be omitted.

[0091]FIG. 5 is a block diagram involving units of calculating quantitycontrolling light quantity and of signal gain setting related to asecond embodiment of the present invention.

[0092] In FIG. 5, the image signals inputted from the signal inputterminal 501 are amplified by an analog amplifying unit 502 constructingan adjusting circuit at an amplifying ratio calculated by a unit ofcalculating amplification ratio 507. Next, subject to conversion intodigital signals with an A/D converter 503, a luminance detection unit504 constructing input image calculating means determines the maximumluminance. Incidentally, in the present embodiment, since the maximumluminance is determined after amplification, the maximum luminance isdetermined in consideration of an amplifying state. Corresponding withthe maximum luminance, a unit of calculating irradiation light quantity505 calculates an irradiation light quantity, and the next unit ofcalculating quantity of controlling light quantity 506 determines acalculating quantity of controlling light quantity. Light quantitycontrolling means are constructed by the unit of calculating lightquantity 505 and the unit of calculating quantity of controlling lightquantity 506. The amplifying ratio is given by the above described unitof calculating amplification ratio 507, and with a result thereof anamplification ratio of the above described analog amplifier isdetermined. The signal processing unit 508 executes respective kinds ofsignal processing other than irradiation light quantity controlling.Signals outputted by the signal processing unit 508 are written into aDMD panel 510 via a DMD driver circuit 509.

[0093]FIG. 5 shows the one to realize the signal gain setting unit inEmbodiment 1 with an analog circuit, and to work well if it comprises anamplifier with a variable amplification ratio and an A/D converter witha variable reference voltage setting.

[0094] Moreover, a method of providing with a reference voltage isdevised so that non-linear amplification will become possible and as aresult thereof, gradation reproducibility will become improvable.

[0095] Amplification of image signals based on light quantitycontrolling at a stage of analog signals prior to undergoing conversionwith an A/D converter will serve to make errors due to quantificationcontrollable compared with Embodiment 1 and also in an image withimproved dynamic range, good image quality with less deterioration ingradation will become available.

[0096] Application of the present invention to a DMD will become able toimprove deterioration in image quality resembling particles due tobinarization processing such as error proliferation, etc. at the side oflow luminance peculiar to the DMD by way of extension of signal levelsin addition to improvement in dynamic range.

[0097] In the present embodiment, a case of a DMD panel has beendescribed, but a case of a liquid crystal panel can be done likewise.

Embodiment 3

[0098]FIG. 6 is a block diagram of a light quantity controlling unit anda signal gain setting unit related to a third embodiment of the presentinvention. In the present embodiment, light quantity controlling isexecuted by feeding back light quantity being illuminated to a lightmodulating element to a calculating unit.

[0099] In FIG. 6, based on image signals inputted from an input end 601,a luminance detection unit 602 calculates luminance distribution and aunit of calculating irradiation light quantity 603 calculatesirradiation light quantity. Next, a unit of calculating quantity ofcontrolling light quantity 604 calculates quantity of controlling lightquantity and an irradiation controlling apparatus 608 drives irradiation609.

[0100] A sensor of detecting irradiation light quantity 610 detectsluminance of irradiation light 609 to be given to the unit ofcalculating quantity of controlling light quantity 604 as well as to thegain calculation unit 605. The gain calculation unit 605 determinesgains to be written into a panel, corresponding with the irradiationlight quantity to be set or the detected irradiation light quantity.Input signals 601 is inputted to the gain unit 606 which changesinput-output features corresponding with coefficients determined by thegain calculation unit 605. The signal processing unit 607 executesrespective kinds of signal processing and transmits image signals to apanel driving circuit (for example, the panel driver 54 in FIG. 1).

[0101] Next, with reference to a flow chart in FIG. 7, aprocessing/controlling method will be described.

[0102] At first, desired irradiation light quantity (S701) determined byimage signals is compared with the light quantity at present (S702)obtainable from the sensor of detecting irradiation light quantity.Here, a trend of change in irradiation light quantity is determinedbased on whether the desired irradiation light quantity is larger or not(S703). Next, time constant calculation means calculate changingquantity per control cycle. Next, changing quantity of irradiation lightquantity corresponding with respective trends is calculated (S705), anda motor is controlled corresponding with that changing quantity (S706).Next, a light quantity detector detects irradiation light quantity aftercontrol (S707) and the stage returns to S701.

[0103] The step S708 calculates a signal level appropriate to lightquantity at present so as to determine amplification ratio for signalsand execute conversion into signals to be written for light modulator(S709). Here, the step S703 may be executed, as shown with a brokenline, based on irradiation light quantity determined at the step S706.

[0104] The sensor to detect the irradiation light is disposed, as shownin a later described embodiment, in such a position that lights insidelight paths or leaked lights can be detected in order to detect lightsin proportion with incident lights to the light modulator.

[0105] Here, in the case where a feedback system as the presentembodiment is not used, this control flow can be used with theirradiation light quantity at present used in the step S702 being avalue having been set previously in the step S707.

[0106] Here, the time constant is determined by motion velocity of amotor and a time period from supply of a control signal to the motor tocompletion of motion corresponding with the control signal, etc.

[0107] Accordingly to the present embodiment, with the sensor to detectthe irradiation light quantity, feedback control is executed so thatsetting of irradiation and setting of signal amplifying ratio willbecome executable accurately, giving rise to an effect that luminance ofthe display image can be controlled stably.

[0108] In addition, in particular, the case where a motor with slowmotion velocity is used or speed control for control of a motor isexecuted with time constants, etc. gives rise to effects.

Embodiment 4

[0109]FIG. 8 is a block construction diagram showing a display apparatusincluding a signal processing apparatus according to the presentinvention. This drawing includes portions in FIG. 1, one beingequivalent to the DSP 57 and others being related to controlling inparticular in the present embodiment. Incidentally, the presentembodiment is arranged to execute synchronization between the displaysignals and the light quantity control timings with a control signaldelay unit 110 separately provided apart from the memory 56 in FIG. 1.In the present embodiment, a case of irradiation light quantity to beilluminated onto the display device such as an LCD, etc. being modulateduniformly on the display device will be described.

[0110] In FIG. 8, reference numeral 101 denotes an image input terminal,reference numeral 102 denotes a gain (dynamic range) controlling unit,reference numeral 103 denotes a signal processing unit, referencenumeral 104 denotes a unit of γ-conversion, reference numeral 105denotes a D/A converter, reference numeral 106 denotes a display devicesuch as an LCD, etc., reference numeral 107 denotes a unit ofcalculating irradiation modulating factor, reference numeral 108 denotesan irradiation modulating device driver and reference numeral 109denotes an irradiation modulating device. In addition, reference numeral110 denotes an image signal delay unit and reference numeral 111 denotesa control signal delay unit.

[0111] The image signals inputted by the image input terminal 101 areinputted to the unit of calculating irradiation modulating factor 107,where quantity of controlling light quantity to be outputted to theirradiation modulating device driver 108 as well as quantity ofcontrolling gain to be outputted to the gain control unit or the γ-unitare calculated.

[0112] With reference to FIG. 9, operation steps inside the unit ofcalculating irradiation modulating factor 107 in FIG. 8 will bedescribed. The image signals inputted by the image input terminal 101 inFIG. 8 are inputted to the unit of calculating irradiation modulatingfactor 107 so that a unit of calculating luminance distribution 107-1calculates luminance distribution. Here, as luminance distribution,maximum value, minimum value, average value and histogram, etc. of imagesignal data of one image plane or a plurality of image planes arecalculated.

[0113] Next, a unit of detecting irradiation light quantity 107-2calculates a light quantity value to become an aim based on a result ofcalculation of luminance distribution. Details on a method forcalculation will be described later. In “processing flow 1” as well as“processing flow 2” to be described later, a flow using the maximumvalue of luminance will be described while in “processing flow 3” amethod using histogram of luminance will be described.

[0114] Next, the unit of calculating quantity of controlling lightquantity 107-3 calculates quantity of controlling light quantity basedon the aimed light quantity value. Here, with the light quantity valueto become an aim being larger than the light quantity value at present,the time constant calculation unit to be described later determines alight quantity control signal so that the light quantity increases onlyby a value determined in advance, and on the contrary with the lightquantity value to become an aim being smaller than the light quantityvalue at present, a light quantity control quantity is determined sothat the light quantity decreases only by a value determined in advance.

[0115] Next, the unit of calculating signal gain 107-4 determines gainas well as off setting of image signals in correspondence with the lightquantity determined by the above described the above described controlsignal. Here, (irradiation light quantity)×(signal gain) is controlledto be always a constant so that brightness of displayed image ismaintained.

[0116] The above described time constant setting unit 107-5 setschanging quantity of light quantity. Here, change rate of light quantitymay be a constant, or may be changed according to a difference between atarget value and the value at present, but in a trailing edge trend (atrend where irradiation light gets dark), image signals are amplified bydecrease in light quantity and luminance to be displayed can bereproduced regardless of speed of control, but in a leading edge trend(a trend where irradiation light gets bright), luminance to be displayedcannot be reproduced by changing image signals if the speed to brightenthe irradiation light is slow. Accordingly, in the present embodiment,the leading edge time constant is made faster than the trailing edgetime constant. Thereby, rapid white display can be reproduced.Incidentally, there are a variety of methods in methods to set changerate of light quantity, but here the change rate is set in terms ofchanging quantity per control cycle.

[0117] Directions of leading edge and trailing edge are detected bymeans to detect trend of change in luminance. The change rate is setsmall so that phenomena resembling flickers taking place in the casewhere a rapid change in irradiation luminance is executed. Incidentally,according to the present embodiment, the control speed of irradiationmight not be so fast in such a direction that light quantity decreases,which has turned out to result in unnatural appearance.

[0118] In addition, in the present embodiment, in order to cope withsuch a problem that images resemble flickering unless bright/dark trendof irradiation is stabilized to a certain degree, the threshold value tocalculate irradiation light quantity from luminance information iscaused to have hysteresis so that stable control is executed by changingthe threshold value in the leading edge trend and the threshold value inthe trailing trend (the leading side should be made larger).

[0119] In addition, there takes place a chronological discrepancybetween the time when the detected image frame is displayed and the timewhen light quantity actually changes. In order to improve this, also inthis embodiment, change in light quantity is synchronized with displayedimages.

[0120] Therefore, the image signal delay unit 110 executes delay bytemporally storing image signals and thereafter outputting them so as todisplay images used for calculation in synchronization with timing whenlight quantity changes.

[0121] The image signal delay unit 110 can be realized with a framememory, etc.

[0122] In addition, instead of delaying image signals, control signalsmay be delayed by the control signal delay unit 111. Although delaytakes place between the calculated image and the image to be controlledactually, this case can be realized with delay elements such as severalflip-flops, etc. without using a frame memory, etc. at lost costs,making it possible to match a change in light quantity with a change ina display image.

[0123] An example of processing flow according to the present embodimentwill be shown as follows.

[0124] In the case where the image signals are constructed with 8 bits,that input signal will be in 256 gradation of 0 to 255. Here, 0 isassigned to black and 255 is assigned to white display.

Processing flow 1

[0125] (1) The maximum values RMAX, GMAX and BMAX inside 1 frame or 1field for each of R, G and B colors are calculated.

[0126] (2) An aimed irradiation light quantity Ltg [%] will be expressedby:

Ltg=RGBmax/255*100

[0127] Wherein, the maximum luminance RGBmax is the largest value amongRMAX, BMAX and GMAX.

[0128] Here, the actual set values for the aimed irradiation lightquantity break down to 10 stages as described below and threshold valuesare caused to have hysteresis.

[0129] In case of a leading edge (irradiation light quantity is madebright):

[0130] RGBmax Ltg

[0131] 230 to 255→100%

[0132] 204 to 229→90%

[0133] 179 to 203→80% to be followed likewise

[0134] In case of a trailing edge (irradiation light quantity is madedark):

[0135] RGBmax Ltg

[0136] 220 to 255→100%

[0137] 194 to 219→90%

[0138] 169 to 193→80% to be followed likewise

[0139] (3) With Dup being changing quantity of light quantity percontrol cycle at the time of leading edge (dark to bright) and with Ddnbeing changing quantity of light quantity per control cycle at the timeof trailing edge (bright to dark),

[0140] The aimed irradiation light quantity and the preceding set lightquantity are compared so that the set irradiation light quantity iscaused to increase in the case where the aimed irradiation lightquantity is greater than the preceding set light quantity. At that time,when difference between the aimed irradiation light quantity and thepreceding set light quantity is larger than Dup, light quantity shouldnot be caused to increase to reach the aimed irradiation light quantityin one control cycle, but increase in light quantity should be limitedto Dup.

[0141] In addition, the aimed irradiation light quantity and thepreceding set light quantity are compared so that the set irradiationlight quantity is caused to decrease in the case where the aimedirradiation light quantity is smaller than the preceding set lightquantity. At that time, when difference between the aimed irradiationlight quantity and the preceding set light quantity is larger than Ddn,light quantity should not be caused to decrease to reach the aimedirradiation light quantity in one control cycle, but decrease in lightquantity should be limited to Ddn.

[0142] An example of program to execute this control process will beexpressed as follows.

Equation 1

[0143] if (aimed irradiation light quantity Ltg) > (preceding set lightquantity Lw(n−1)) then if((Ltg-Lw(n−1)) >Dup)then set irradiation lightquantity Lw(n) =Lw(n−1) +Dup else Lw(n) =Ltg end if elseif((Lw(n−1)-Ltg) >Ddn) then set irradiation light quantity Lw(n)=Lw(n−1) +Ddn else Lw(n) =Ltg end if end if

[0144] (4) Setting of a pulse motor as well as setting of a signal gaincorresponding with the set irradiation light quantity is executed insynchronization with vertical synchronization signal VD.

[0145] (5) The above described (1), (2), (3) and (4) are repeated inevery ΔT time.

[0146] Here, ΔT depends on motion speed of the means to control lightquantity, and here on motion speed of the motor to rotate the polarizingplate to change light quantity, but for this processing flow, with amotor having sufficient speed, one frame interval is taken as a controlcycle. In addition, in the case where one frame is constructed with aplurality of fields, a field interval is preferably taken.

Processing flow 2

[0147] In addition, in the case where motion speed of the motor isslower compared with the frame rate, the following flow may be used torealize light quantity control effectively.

[0148] (1) The same as the above described processing flow 1.

[0149] (2) The same as the above described processing flow 1.

[0150] (3) The set light quantity Lw(n)=Ltg

[0151] (4) Setting of the pulse motor is set corresponding with the setlight quantity.

[0152] Here, as for setting of the signal gain, setting is repeatedlinearly to reach the aimed value in correspondence with change inirradiation light quantity, in synchronization with VD, during theperiod when the pulse motor reaches the set value.

[0153] (5) After the pulse motor reaches the set value, the abovedescribed (1), (2), (3), and (4) are repeated.

[0154] As described so far, also in the case where motion speed of themotor is slow, display luminance will become maintainable constantly.

Processing flow 3

[0155] A processing method with histogram of luminance distribution willbe described.

[0156] (1) An input signal is divided into n units with threshold valuesA0 to A(n−1) of the comparator, and the number of signals withinrespective ranges are counted so that luminance distribution is created.The n-divided count number should be C0 to Cn respectively. Here,A(n−1)>A(n−2)>. . . >A0.

[0157] (2) Next, the light quantity value to become an aim is calculatedby judging whether or not the number is more than a predetermined numbersequentially in an order of luminance intensity from a range with largevalue.

[0158] Here the actual set value is caused to have hysteresis in thethreshold value with the aimed irradiation light quantity consisting of10 stages as described below.

[0159] In case of a leading edge (irradiation light quantity is madebright):

Equation 2

[0160] if (Cn> (100+ΔH)) then aimed irradiation light quantity Ltg<=100%elsif ((C(n) +C(n−1)) > (100+ΔH)) then aimed irradiation light quantityLtg<=90% elsif ((C(n) +C(n−1) +C(n−2)) > (100+ΔH)) then aimedirradiation light quantity Ltg<=80% to be followed likewise.

[0161] In case of a trailing edge (irradiation light quantity is madebright):

Equation 3

[0162] if (Cn>100) then aimed irradiation light quantity Ltg<=100% elsif((C(n) +C(n−1)) >100) then aimed irradiation light quantity Ltg<=90%elsif ((C(n) +C(n−1) +C(n−2)) >100) then aimed irradiation lightquantity Ltg<=80% to be followed likewise.

[0163] Here, comparative value as well as hysteresis quantity ΔH may bechanged every count value executing comparison.

[0164] (3) The same as the above described processing flow 1 or 2.

[0165] (4) The same as the above described processing flow 1 or 2.

[0166] (5) The same as the above described processing flow 1 or 2.

[0167] As described so far, according to the present embodiment, theaimed irradiation light quantity is divided into n units, and thethreshold value being a judgment value for determining the irradiationlight quantity is caused to have hysteresis with the control trend ofirradiation light quantity so that the phenomena causing changes inirradiation light quantity to occur frequently in the vicinity of thethreshold value may disappear, enabling stable images to becomeavailable and improving image quality further.

[0168] In addition, the time constant setting unit is provided withfunction of controlling time base changing quantity, in particular, afunction to adjust time to practically create changes in light quantityper control cycle so that velocity of changes in light quantity toward alamp can be controlled (limited), making suitable display realizable.

[0169] In addition, irradiation control means with motion speed beingslow can be used and are advantageous in terms of costs.

[0170] In addition, phenomena like flickers will become controllable.

[0171] Thus, according to levels (distribution, features) of inputtedimage signals, irradiation light quantity is made variable, and means toconvert gains or voltage-luminance feature of image signals incorrespondence with the irradiation light quantity are provided so thatit becomes possible to improve dynamic range while keeping the displayedluminance.

Embodiment 5

[0172] Next, a fifth embodiment of the present invention will bedescribed.

[0173]FIG. 10 is a schematic view showing a construction of an opticalsystem of a liquid crystal projector related to the fifth embodiment ofthe present invention, in which reference numeral 1 denotes a reflectorfor a lamp, reference numeral 2 denotes an arc tube (lamp), referencenumeral 3 denotes a fly-eye integrator, reference numeral 4 denotes a PSconversion optical element and reference numeral 5 denotes a irradiationlight quantity modulator. In the irradiation light quantity modulator 5,a phase plate or a polarizing plate is attached to a ultrasonic motor.Reference numerals 6 and 24 denote relay lenses, reference numerals 7,9, 11 and 12 denote mirrors, reference numerals 8 and 10 denote adichroic mirror, reference numerals 13, 14 and 15 denote field lenses,reference numerals 16, 17 and 18 denote liquid crystal panels, referencenumerals 19, 20 and 21 denote polarizing plates, reference numeral 22denotes a cross prism and reference numeral 23 denotes a projectionlens.

[0174] A principle on how irradiation light quantity to the liquidcrystal panels 16, 17 and 18 is modulated will be described withreference to FIG. 10. The light fluxes 25 emitted from the lamp 2 arereflected by the reflector 1 to become parallel light fluxes 26. In thepresent embodiment, the shape of the reflector 1 is parabolic,converting lights into parallel light fluxes, but it goes without sayingthat the shape of the reflector is made oval, converting lights into acondensed light flux. The above described light flux 26 is emitted intothe fly-eye integrator 3, and respective fly-eye lenses 3a in theincident side keeps cooperative relationship with the liquid crystalpanels. This integrator 3 serves to unify distribution of light fluxemitted from the lamp 2, and, in addition, to simultaneously unify colordistribution for respective light emitting areas of the lamp 2.

[0175] The light flux emitted from the integrator 3 is non-polarizedlight flux and is converted into a linear polarized flight flux with thePS conversion element 4. As these PS conversion elements, thoseconstructed by polarized beam splitters and ½-wavelength plates can beused. The case of this system sufficiently gives rise to the ratio of Plight and S light of not less than 20:1.

[0176] When this linearly polarized light flux passes by the opticalelement 5 constructed to rotate the polarized plate or the phase platecontinually, the irradiation light quantity to the liquid crystal panelscontinually changes.

[0177] In the case where a polarizing plate is used for the opticalelement 5, light quantity (approximately 85%) with exclusion ofapproximately 15% being an absorbed surface reflection component withthe polarizing plate when the linear polarizing trend after passing theabove described PS conversion element 4 and the polarizer trend of thepolarizing plate are disposed in parallel.

[0178] When the polarizing plate is rotated toward the polarizing trendof the above described linear polarized light flux, only projectingcomponent toward the trend of polarizer of the polarizing plate istransmitted so that light quantity can be reduced continually. In thecase where the PS ratio of the linearly polarized light flux emittedinto the above described optical element 5 is 20:1, irradiation lightquantity to the panels could be changed to 1/20.

[0179] As described above, after passing the PS conversion element 4,the light flux is converted into linearly polarized light (could bepartially linear conversion), and thereafter the polarizing platethrough which the linearly polarized light passes is rotated so that theirradiation light quantity onto the panel can be changed. Thispolarizing plate may basically be disposed anywhere after the PSconversion, but is desirably disposed apart from the light source sincelight quantity is so intensive when it is disposed near the source thatthe polarizing plate itself changes in quality. In addition, in the casewhere it is difficult to dispose it apart from the light source, apolarizing plate made of sapphire can be used to improve itslight-resistant and heat-resistant nature.

[0180] The above described polarizing plate is rotated with anultrasonic motor. The ultrasonic motor (USM) is well controlled at ahigh speed and in terms of rotary angle, and is suitable for lightquantity adjustment for the present objective.

[0181] For rotation speed of the ultrasonic motor, which depends on loadtorque, nevertheless 1000 to 5000 rpm is sufficiently attainable, andwith rotary angle of 90° (equivalent to white-to-black conversion),irradiation light quantity can be changed in 3 to 15 ms. Image signalsscarcely change from white to black rapidly, and with light quantitychange of 10%, a necessary rotary angle is 26° and the irradiation lightquantity change speed in that case is 1 to 5 ms, being faster than theresponse speed 10 to 20 ms of liquid crystal. As for rotary accuracy,rotary angle can be controlled with an encoder mounted on the motor andsufficient accuracy within a range of ±0.1° has been obtained.

[0182] As a motor, besides the ultrasonic motor, equivalent speed andaccuracy is realizable with a stepping motor.

[0183] The above described example is a system in which later-describeddesired irradiation light quantity is calculated from image signals, anda rotary angle of polarizing plate for realizing that determinedirradiation light quantity is calculated to operate the motor so as toprovide that rotary angle.

[0184] Next, a system in which the irradiation light quantity itself ismonitored, undergoes servo to be controlled to a desired light quantitywill be described with reference to FIG. 11. An optical system in FIG.11 excludes the mirror 7 for the one in FIG. 10 which has been replacedwith a half mirror 1101, and adds thereto a condenser 1102 to condenselights having transmitted through the half mirror 1101 and lightquantity detector 1103 to detect that light quantity. The half mirror1101 may be constructed to be approximately reflexive with reflectingcomponent of 99% and penetrating component of 1%. Accordingly,irradiation light quantity to the panels drops slightly with this halfmirror, which however is not a level to become a problem. Penetratinglight flux from the half mirror 1101 enters the light quantity detector1103 via the condenser 1102.

[0185] A method to control irradiation light quantity to the panels inthe optical system in FIG. 11 will be described with reference to a flowchart in FIG. 12. The subsequent irradiation light quantity isdetermined to be set at which level based on the irradiation lightquantity calculated from image signals and the irradiation lightquantity at present. The irradiation light quantity at present is takeninto consideration, because even if luminance levels change rapidly fromwhite to black due to change of scene, the change should not be kept upwith rapidly, and moderate change at several fields to several tens offields had better be taken to easily execute operations and the like onthe liquid crystal panels, etc., which are visible to human eyes withoutcausing any uncomfortable feeling, and are adaptable to such cases.

[0186] After the above described level of irradiation light quantity isdetermined, the motor is rotated so as to provide with that irradiationlevel so that actual light quantity after control is measured with thelight quantity detector 1103. Due to the light which is condensed by thecondenser 1102, the detector which itself is a small sized pin type onewill work sufficiently, and can detect light quantity in several 10 μsin combination with a rapid amplifier. If the motor is controlled tomake this light quantity to reach a desired level, irradiation withconstant light quantity is realized and a stable image plane is realizedeven if change in light quantity takes place in the lamp itself. Inparticular, in case of using a very high pressure mercury lamp and ametal halide lamp being effective to make a project engine smaller andhaving arc length being short with 1 to 1.3 mm, movement of the emissionarea of the lamp 2 could give rise to change in light quantity emittedinto the integrator 3 and change in practical irradiation light quantityto the panels, resulting in deteriorating display performance, andsettlement on that has been demanded, and now that can be dealt witheffectively and display performance can be advantageously improved.

[0187] In addition, signals corresponding with actually detected lightquantity are calculated to be written in the liquid crystal panels,etc., enabling such operation that switches irradiation light slowly forchange in image from white to black and fast for change from black towhite. This serves to secure a peak luminance of white for change fromblack to white, giving rise to advantages that not only displayperformance is improved but also load on the motor is reduced, consumedpower saving becomes possible and life of the motor is extended.

[0188] Here, an ultrasonic motor is used to rotate the polarizing plateto execute irradiation light quantity control that is rapid, without anybacklash, and is excellent in calmness. However, it goes without sayingthat another motor other than the ultrasonic motor is usable.

[0189] The above described construction controlled irradiation lightquantity with rotation of the polarizing plate, but instead of thispolarizing plate, uses a phase plate which gives rise to few lightquantity losses and is suitable as a high luminance projector. As thephase plate, a λ/2 plate is adopted so that the phase of the linearpolarized light flux after passing the λ/2 plate rotates by 2θ incorrespondence with the rotary angle θ of the λ/2 plate toward a linearpolarized light flux emitted from the PS conversion element 4.Accordingly, the rotary angle of the λ/2 plate may be a half toward thepolarizing plate, enabling more rapid light quantity modulation. Thelight quantity of the rotated polarized light flux suffers from losswith the phase plate is 2 to 3% at most, and is excellent in providingwith high luminance. The polarizing plate preceding the liquid crystalpanel illuminates only that inclined projection component to the liquidcrystal panels, and thus irradiation light quantity can be modulated.

[0190] In the optical system in FIG. 10 and FIG. 11, the light fluxhaving transmitted through the optical element for irradiation lightquantity modulation (irradiation light quantity modulator) 5 isilluminated to the liquid crystal panels for respective color via relaylenses 6 and 24. The dichroic mirror 8 transmits the blue color butreflects others. The dichroic mirror 10 transmits the red color andreflects the green color. In this case, reference numeral 16 denotes theliquid crystal panel for the blue color, reference numeral 17 denotesthe liquid crystal panel for the green color and reference numeral 18denotes the liquid crystal panel for the red color, which is for examplea TN liquid crystal panel to be driven with a TFT. Moreover, as concernsthe one with micro lenses for respective pixels, shading of lights atthe opening decreases and provision of high luminance has been planned.

[0191] Accompanied by irradiation light quantity conversion, a newmethod is adopted also for driving the above described liquid crystalpanels. This driving method will be described later. The light fluxesfor respective colors subject to modulation with the respective colorliquid crystal panels are synthesized with the cross prism 22 and areshown on image plane via the projection lens 23.

Embodiment 6

[0192]FIG. 13 is a schematic view showing a sixth embodiment of thepresent invention. In FIG. 13, lights emitted from a light source 1301such as a metal halide lamp and a xenon lamp, ext. are made to goapproximately in parallel with the parabolic reflector 1302 and subjectto reflection on the mirror 1303, and form a light source image in theposition of the front end surface (a first end surface) 1305-1 of theintegrator 1305 via the condenser 1304. In the vicinity of this lightsource image, a diaphragm indicated by 1310 is provided. When thediaphragm 1310 is restricted, incident light quantity for the integrator1305 can be decreased. In the light flux emitted into the integrator105, a portion transmitted through the integrator and a portion of theremaining portion is emitted from the rear end surface (a second endsurface) 1305-2 subject to one to several reflections on the internalreflection surface.

[0193] It is advisable that a parabolic reflector 1302 and a condenser1304 fulfilling 4≦F4/F3≦10, (where F3 is distance from the bottomsurface of the above described parabolic reflector to the abovedescribed focus) with F3 being the focal distance of the parabolicreflector 1302 and F4 being the focal distance of the condenser 1304.The reason thereof is that a small light source image can be formed inthe front end surface position 1305-1 of the integrator 1305. The lightflux from the integrator 1305 is emitted into the convex lens 1306,transmitted therethrough the dichroic filter 1311 which only RGB or RGBWlights transmitted therethrough, and forms the image of the light source1301 in the vicinity of the reflection mirror 1307. The above describeddichroic filter is exemplified by a penetration type, but it goeswithout saying that a reflection type is effectively used. Thereflection mirror 1307 is disposed in a position of the openingdiaphragm 1313 of the projection lens 1314.

[0194] In FIG. 13, the light flux from the integrator 1305 is reflectedby the reflection mirror 1307 and is emitted to a plane convex lens 1308so as to be made to become approximately parallel lights with the planeconvex lens 1308 and to illuminate the DMD panel 1309 being a lightmodulator. The DMD panel 1309 forms image information by lightmodulation such as scattering or non-scattering of incident lights foreach pixel corresponding with image signals. The liquid crystal displaypanel of the above described fifth embodiment has similar constructionand functions, and as necessity arises an liquid crystal display panelof another type can be used.

[0195] An important point in the optical system of the presentembodiment is that a convex lens 1306 being the rear end surface of theintegrator 1305 and the plane convex lens 1308 form an image on the DMDpanel 1309. In the rear end surface 1305-2 of the integrator 1305, thelight flux penetrating inside the integrator 1305 without any reflectionand the light fluxes subject to one or several reflections areoverlapped, and thereby unevenness in color and unevenness in luminancedoes not take place to give rise to approximately uniform lightintensity distribution. Accordingly, if this rear end surface 1305-2 isbrought into cooperative relationship with the display surface of theDMD panel 1309 by way of the convex lens 1306 and the plane convex lens1308, display surface of the DMD panel alleviate unevenness in color andunevenness in luminance and as a result thereof, unevenness in color andunevenness in luminance of images displayed on the image plane 1315 arealleviated. In addition, the shape of the rear end surface 1305-2 of theintegrator 1305 is made to be a rectangular approximately similar inshape with the display surface of the DMD panel 1309 so that the rearend surface 1305-2 of the integrator 1305 is made to form an image onthe DMD panel 1309 at an appropriate magnifying ratio to illuminate thepanel efficiently.

[0196] Incidentally, in FIG. 13, the lens 1304, the lens 1306 and thelens 1308 are respectively one lenses, but these lens system can beconstructed by a plurality of lenses respectively. Respective lenses ofthe above described embodiments are constructed likewise. Accordingly,the term referred to as “convex lens” in the present application is alens system having positive refraction force.

[0197] With the DMD panel 1309, the reflection lights of respectivecolors modulated corresponding with image signals are condensed by theplane convex lens 1308, and at least a portion of the flux passes theopening of the opening diaphragm 1313 and is projected on the imageplane 1315 via the projection lens 1314. At this time, in the opening ofthe diaphragm 1313, a light source image similar in shape with the lightsource image is formed with the light subject to regular reflection bythe DMD panel 1309. The reason hereof is that the light source 1301, thefront end surface 1305-1 of the integrator 1305, the reflection mirror1307 and the opening diaphragm 1313 are disposed in a cooperativepositions each other. The optical system consisting of the projectionlens 1314 and the condenser 1308 is a system that is telecentric in theDMD panel side.

[0198] The present embodiment is a system to display RGB with timedivision by way of rotation of the dichroic filter 1311 shown in FIG.13, and the diaphragm 1310 for light quantity adjustment is modulated insynchronization with one rotation so that luminance modulation similarto the fifth embodiment can be executed. In addition, the diaphragm 1310is adjusted in synchronization with respective color levels of the RGBtime division so that irradiation light quantity can be also modulated.

[0199] The present construction is advantageous in costing little eitherto execute irradiation light quantity modulation to provide the highdynamic range DMD with further highly dynamic range high image quality.

[0200] The above described embodiment has been exemplified by the DMDpanel, but it goes without saying that the liquid crystal panels areeffective in this respect.

Embodiment 7

[0201]FIGS. 14A and 14B are block diagrams showing an electric systemrelated to a seventh embodiment of the present invention. In FIGS. 14Aand 14B, reference numeral 1400 denotes a DMD and reference numeral 1401denotes a DMD driver unit. The driver unit 1401 comprises internally aunit 1402 of signal conversion processing such as time division, etc., amemory 1403, a control unit 1404 and a reset driver 1405.

[0202] Coupled with signal processing, there is a color filter system1406 (corresponding to 1311 in FIG. 13), which is constituted by controlon rotation synchronization and servo 1407 as well as the color filter1408 itself.

[0203] The diaphragm 1409, the power source unit 1410 and the DMD driverunit 1401 are connected with the micro computer 1462 and are controlledin their entirety.

[0204] The power source unit 1410 consists of the ballast 1411, thepower source 1412, the lamp 1413, the lamp fan 1414 and the fan forcooling the power source and the electronic substrate 1415. In addition,a user interface unit 1416 comprising a remote controller and buttons isconstructed by the remote controller 1417, the LED 1418 to emit lightsfrom the remote controller, buttons and keys 1419, and switches 1420.

[0205] The acoustic system 1421 comprises a DA unit 1422 to DA convertoutput signals of digital signals 1/F such as LVDS and TMDS, a volume(VOL) adjusting circuit 1423, an amplifier 1424 and speakers 1425.

[0206] As a monitoring function 1461, an S terminal 1426, a componentvideo terminal 1427, a composite video terminal 1428 and a terminal fordigital broadcasting (D3) 1429, etc. are provided.

[0207] On the other hand, analog signals from the PC are inputted fromthe Dsub 15 pins 1430; converted into digital signals at the ADconverter 1434 via phase adjustment 1431, PLL 1432 and the preamplifier1433; and enter a scan converter 1436 via a multiplexer 1435.

[0208] In addition, signals for DTV enter the scan converter 1436 via atuner unit 1437 and an MPEG decoder 1438. Normal NTSC signals areinputted via the scan converter 1436 after AD conversion in the ADconverter 1451. In addition, audio signals separated from signals forDTV and NTSC signals enter the transmission unit 1455 of an LVDSinterface via a multiplexer 1452. Video signals from the scan converter1436 and audio signals from the multiplexer 1452 enter a front end 1454and an acoustic system 1421 via the transmission unit 1455 of the LVDSinterface and the receiver unit 1453. Output signals of the front end1454 enter the DMD driver unit 1401.

[0209] The present construction not only makes high image qualityavailable for a front projector and a rear projector for office use butalso is applicable to rear or front TVs with large image planes forconsumer use, home theaters and mini theaters, etc.

[0210] In FIGS. 14A and 14B, the DTV tuner unit 1463 comprises a tuner1464, an SAW filter 1439, an AD converter 1440, a VSB demodulator 1441and a demixer 1442. An MPEG decoder 1438 comprises a video decoder 1443and an audio decoder 1444. An NTSC tuner 1445 comprises a tuner 1446, anSAW filter 1447, an NTSC demodulator 1448, an audio decoder 1449 and anAD converter 1450.

[0211] As described so far, according to the embodiment of the presentinvention, the irradiation light quantity control means are provided toadjust light quantity illuminated to the light modulator so that a darkimage plane can be illuminated with low light quantity while a brightimage plane can be illuminated with high light quantity, and as aresult, contrast higher than in the case of irradiating the lightmodulator at a constant light quantity can be realized.

[0212] According to the embodiment of the present invention, theirradiation light quantity modulating means have been provided betweenthe light source and the light modulator so that a dark image plane canbe illuminated with low light quantity while a bright image plane can beilluminated with high light quantity, and as a result, contrast higherthan in the case of irradiating the light modulator at a constant lightquantity can be realized.

[0213] According to the embodiment of the present invention, theirradiation light quantity modulating means have been provided todirectly control the light source emitting lights to be illuminated tothe light modulator so that a dark image plane can be illuminated withlow light quantity while a bright image plane can be illuminated withhigh light quantity, and as a result, contrast higher than in the caseof irradiating the light modulator at a constant light quantity can berealized.

[0214] According to the embodiment of the present invention, lightquantity is controlled to keep relationship approximately in inverseproportion to signal amplifying ratio so that high contrast can berealized while display luminance in an intermediate gradation is kept ata constant.

[0215] As described in the embodiments in particular so far, accordingto the invention of the present application, image display with highimage quality can be realized.

What is claimed is:
 1. A display apparatus for irradiating with lightgenerated by a light source a light modulating element and forming adisplay image plane from the light which is transmitted through orreflected by the light modulating element, comprising: input imagecalculating means for performing predetermined calculation according toan input display signal; light quantity controlling means forcontrolling light quantity irradiated onto said light modulating elementaccording to a result of said calculation; and a memory for storing thedisplay signal subjected to the calculation by said input imagecalculating means, and thereafter for outputting the display signal tosaid light modulating element.
 2. A display apparatus for irradiatinglight generated by a light source onto a light modulating elementinputting modulated signal formulated by converting a display signalinputted in an analog state into digital display signals and thereaftersubjecting the digital display signal to a predetermined processing, andfor forming a display image plane from the light transmitted through orreflected by the light modulating element, comprising: input imagecalculating means for performing predetermined calculation according tothe display signal; light quantity controlling means for controllinglight quantity irradiated onto said light modulating element accordingto a result of said calculation; and an adjusting circuit for adjustingthe display signal according to a result of the calculation, whereinsaid adjusting circuit adjusts the display signal before the displaysignal in said analog state are converted into digital display signal.3. A display apparatus for irradiating light generated by a light sourceonto a light modulating element, and for forming a display image planewith the light transmitted through or reflected by the light modulatingelement, comprising: input image calculating means for performing apredetermined calculation according to an input display signal; andlight quantity controlling means for controlling light quantityirradiated onto said light modulating element according to a result ofthe calculation, wherein said light quantity controlling means sets achange rate of light quantity, such that the change rate at decreasingthe light quantity is smaller than a change rate at increasing the lightquantity.
 4. A display apparatus for irradiating light generated by alight source onto a light modulating element, and for forming a displayimage plane from the light transmitted though or reflected by said lightmodulating element, comprising: input image calculating means forperforming a predetermined calculation according to an input displaysignals; and light quantity controlling means for increasing ordecreasing a light quantity irradiated onto said light modulatingelement step by step according to a value determined by result of saidcalculation, wherein a threshold value at which said light quantitycontrolling means increases the light quantity from a first stage beinga predetermined stage into a second stage increased therefrom by onestep according to the calculation is different from a threshold value atwhich said light quantity controlling means decreases the light quantityfrom the second stage into a stage of smaller light quantity.
 5. Thedisplay apparatus according to claim 4, wherein said light quantitycontrolling means set so as to increase said light quantity from saidfirst stage to said second stage when the value determined by saidcalculation changes in the first direction to exceed the first thresholdvalue, and so as to decrease said light quantity from said second stageto a stage of a low light quantity when the value determined by saidcalculation changes in the second direction being opposite against saidfirst direction to exceed the second threshold value set in the side ofsaid second direction than said first threshold value.
 6. The displayapparatus according to claim 5, wherein the stage of the low lightquantity is said first stage.
 7. The display apparatus according toclaim 1, further comprising an adjusting circuit for adjusting displaysignal according to a result of the calculation.
 8. The displayapparatus according to claim 3, further comprising an adjusting circuitfor adjusting display signal according to a result of the calculation.9. The display apparatus according to claim 4, further comprising anadjusting circuit for adjusting display signal according to a result ofthe calculation.
 10. The display apparatus according to claim 1, whereinsaid calculation is calculation to give maximum luminance in saiddisplay signals inputted within a predetermined period.
 11. The displayapparatus according to claim 2, wherein said calculation is calculationto give maximum luminance in said display signals inputted within apredetermined period.
 12. The display apparatus according to claim 3,wherein said calculation is calculation to give maximum luminance insaid display signals inputted within a predetermined period.
 13. Thedisplay apparatus according to claim 4, wherein said calculation iscalculation to give maximum luminance in said display signals inputtedwithin a predetermined period.
 14. The display apparatus according toclaim 1, wherein said calculation is calculation to give a number ofdata exceeding a predetermined luminance among luminance data includedin said display signals inputted within a predetermined period include.15. The display apparatus according to claim 2, wherein said calculationis calculation to give a number of data exceeding a predeterminedluminance among luminance data included in said display signals inputtedwithin a predetermined period include.
 16. The display apparatusaccording to claim 3, wherein said calculation is calculation to give anumber of data exceeding a predetermined luminance among luminance dataincluded in said display signals inputted within a predetermined periodinclude.
 17. The display apparatus according to claim 4, wherein saidcalculation is calculation to give a number of data exceeding apredetermined luminance among luminance data included in said displaysignals inputted within a predetermined period include.
 18. The displayapparatus according to claim 1, further comprising sensors for detectinglight quantity irradiated onto said light modulating element, whereinsaid light quantity controlling means controls the light quantity basedon the calculation results and a detection results by said sensors. 19.The display apparatus according to claim 2, further comprising sensorsfor detecting light quantity irradiated onto said light modulatingelement, wherein said light quantity controlling means controls thelight quantity based on the calculation results and a detection resultsby said sensors.
 20. The display apparatus according to claim 3, furthercomprising sensors for detecting light quantity irradiated onto saidlight modulating element, wherein said light quantity controlling meanscontrols the light quantity based on the calculation results and adetection results by said sensors.
 21. The display apparatus accordingto claim 4, further comprising sensors for detecting light quantityirradiated onto said light modulating element, wherein said lightquantity controlling means controls the light quantity based on thecalculation results and a detection results by said sensors.
 22. Thedisplay apparatus according to claim 1, comprising an adjusting circuitfor adjusting display signal according to said calculation result, and asensor for detecting light quantity irradiated onto said lightmodulating element, wherein said adjusting circuit performing theadjustment according to the calculation result and the detection resultby said sensor.
 23. The display apparatus according to claim 3,comprising an adjusting circuit for adjusting display signal accordingto said calculation result, and a sensor for detecting light quantityirradiated onto said light modulating element, wherein said adjustingcircuit performing the adjustment according to the calculation resultand the detection result by said sensor.
 24. The display apparatusaccording to claim 4, comprising an adjusting circuit for adjustingdisplay signal according to said calculation result, and a sensor fordetecting light quantity irradiated onto said light modulating element,wherein said adjusting circuit performing the adjustment according tothe calculation result and the detection result by said sensor.
 25. Thedisplay apparatus according to claim 1, comprising means for settingquantity of changing irradiation light quantity, so as to set changingquantity or change rate of said irradiating light quantity.
 26. Thedisplay apparatus according to claim 2, comprising means for settingquantity of changing irradiation light quantity, so as to set changingquantity or change rate of said irradiating light quantity.
 27. Thedisplay apparatus according to claim 3, comprising means for settingquantity of changing irradiation light quantity, so as to set changingquantity or change rate of said irradiating light quantity.
 28. Thedisplay apparatus according to claim 4, comprising means for settingquantity of changing irradiation light quantity, so as to set changingquantity or change rate of said irradiating light quantity.
 29. Thedisplay apparatus according to claim 26, wherein said change rate isgreater in a trend to increase irradiation light quantity than in atrend to decrease irradiation light quantity.
 30. The display apparatusaccording to claim 28, wherein said change rate is greater in a trend toincrease irradiation light quantity than in a trend to decreaseirradiation light quantity.
 31. The display apparatus according to claim1, wherein said light quantity controlling means are means to bedisposed between said light source and said light modulating element tocontrol light quantity to be irradiated onto said light modulatingelement from said light source.
 32. The display apparatus according toclaim 2, wherein said light quantity controlling means are means to bedisposed between said light source and said light modulating element tocontrol light quantity to be irradiated onto said light modulatingelement from said light source.
 33. The display apparatus according toclaim 3, wherein said light quantity controlling means are means to bedisposed between said light source and said light modulating element tocontrol light quantity to be irradiated onto said light modulatingelement from said light source.
 34. The display apparatus according toclaim 4, wherein said light quantity controlling means are means to bedisposed between said light source and said light modulating element tocontrol light quantity to be irradiated onto said light modulatingelement from said light source.
 35. The display apparatus according toclaim 1, wherein said light quantity controlling means is means tocontrol voltage or current to be supplied to said light source.
 36. Thedisplay apparatus according to claim 2, wherein said light quantitycontrolling means is means to control voltage or current to be suppliedto said light source.
 37. The display apparatus according to claim 3,wherein said light quantity controlling means is means to controlvoltage or current to be supplied to said light source.
 38. The displayapparatus according to claim 4, wherein said light quantity controllingmeans is means to control voltage or current to be supplied to saidlight source.
 39. An image signal processing apparatus used in a displayapparatus for irradiating light generated by a light source onto a lightmodulating element, and for forming a display image plane from the lighttransmitted through or reflected by said light modulating element,comprising: input image calculating means to performing predeterminedcalculation according to an input display signal; means for outputting acontrol value for controlling light quantity irradiated onto said lightmodulating element according to a result of the calculation; and amemory for storing display signal subjected to the calculation by saidinput image calculating means, and thereafter outputting the displaysignal to said light modulating element.
 40. An image signal processingapparatus used in a display apparatus for irradiating light generated bya light source onto a light modulating element inputting modulatedsignal formed by converting a display signals inputted in an analogstate into digital display signals and thereafter subjecting theconverted digital signal to a predetermined processing, and for forminga display image plane from the light transmitted through or reflected bysaid light modulating element, comprising: input image calculating meansfor performing predetermined calculation according to a display signal;means for outputting a control value for controlling light quantityirradiated onto said light modulating element according to a result ofthe calculation; and an adjusting circuit for adjusting display signalaccording to a result of the calculation, wherein said adjusting circuitadjusts display signal before the conversion of the display signals insaid analog state into digital display signals.
 41. An image signalprocessing apparatus used in a display apparatus for irradiating lightgenerated by a light source onto a light modulating element, and forforming a display image plane from the light transmitted through orreflected by said light modulating element, comprising: input imagecalculating means for performing predetermined calculation according toan input display signal; and means for outputting a control value tocontrol light quantity irradiated onto said light modulating elementaccording to a result of the calculation; and wherein said control valueis set such that a change rate at decreasing the light quantity issmaller than a change rate at increasing the light quantity.
 42. Animage signal processing apparatus used in a display apparatus forirradiating light generated by a light source onto a light modulatingelement, and for forming a display image plane from the lighttransmitted through or reflected by said light modulating element,comprising: input image calculating means for performing predeterminedcalculation according to an input display signal; and means foroutputting a control value to increase or decrease a light quantityirradiated onto said light modulating element step by step according toa value determined by result of the calculation, wherein a thresholdvalue at which said means for outputting a control value outputs acontrol value to increase a first stage being a predetermined stage intoa second stage by increasing said light quantity by one stepcorresponding to a value determined by said calculation is differentfrom a threshold value at which said means output a control valuedecreased from the second stage into a stage with less light quantity.